1. Field of the Invention
This invention relates generally to spatial light modulators (SLMs). More particularly, it relates to the design and fabrication of elastomer spatial light modulators for maskless extreme ultraviolet (EUV) lithography.
2. Description of the Related Art
Extreme Ultraviolet (EUV) lithography is considered by pioneering researchers as a leading possibility for delineating structures smaller than 100 nm. Because defect free EUV masks are expensive, difficult to obtain, and cannot be protected by pellicles due to high absorption in the EUV, maskless EUV lithography appears to be a promising alternative. An effort has been made to use spatial light modulators (SLMs) to replace masks, see, N. Choksi et al. “Maskless Extreme Ultraviolet Lithography,” J. Vac. Sci. Technol. B 17, pp. 3047–3051 (1999).
EUV lithography, maskless lithography, and SLMs are known in their respective fields and therefore are not further described herein for the sake of brevity. Readers are directed to the following U.S. patents and articles for related teachings in the respective fields.    1. U.S. Pat. No. 4,494,826, “SURFACE DEFORMATION IMAGE DEVICE.”    2. U.S. Pat. No. 4,529,620, “METHOD OF MAKING DEFORMABLE LIGHT MODULATOR STRUCTURE.”    3. U.S. Pat. No. 4,566,935, “SPATIAL LIGHT MODULATOR AND METHOD.”    4. U.S. Pat. No. 5,311,360, “METHOD AND APPARATUS FOR MODULATING A LIGHT BEAM.”    5. U.S. Pat. No. 5,867,301, “PHASE MODULATING DEVICE.”    6. U.S. Pat. No. 5,870,176, “Maskless lithography.”    7. U.S. Pat. No. 6,060,224, “METHOD FOR MASKLESS LITHOGRAPHY.”    8. U.S. Pat. No. 6,356,340, “PIEZO PROGRAMMABLE RETICLE FOR EUV LITHOGRAPHY.”    9. U.S. Pat. No. 6,544,698, “MASKLESS 2-D AND 3-D PATTERN GENERATION PHOTOLITHOGRAPHY.”    10. C. W. Gwyn et al. “Extreme Ultraviolet Lithography,”J. Vac. Sci. Technol. B 16, pp.3142–3149 (1998).    11. Y. Shroff et al. “Fabrication of Parallel-Plate Nanomirror Arrays For Extreme Ultraviolet Maskless Lithography,”J. Vac. Sci. Technol. B 19, pp. 2412–2415 (2001).    12. O. Solgaard et al. “Deformable Grating Optical Modulator,” Opt. Lett. 17, pp. 688–690. (1992).    13. R. Tepe et al. “Viscoelastic Spatial Light Modulator with Active Matrix Addressing,” App. Opt. 28, pp. 4826–4834 (1989).    14. W. Brinker et al. “Metallized Viscoelastic Control Layers for Light-Valve Projection Displays,” Displays 16, pp. 13–20 (1995).    15. S. Sakarya et al. “Technology of Reflective Membranes for Spatial Light Modulators,” Sens. and Actuators A 97–98, pp. 468–472 (2002).    16. R. Tepe “Theoretical Analysis of an Electrically Addressed Viscoelastic Spatial Light Modulator,” J. Opt. Soc. Am. A 4, pp. 1273–1282 (1987).    17. P. Duerr et al. “Characterization of Spatial Light Modulators for Microlithography,” Proc. SPIE 4985, pp. 211–221 (2003).    18. H. Kueck et al. “New system for fast submicron laser direct writing,” Proc. SPIE 2440, pp. 506–514 (1995).    19. Y. Chen et al. “Modeling and Control of Nanomirrors for EUV Maskless Lithography,” Technical Proceedings of the Third Intl. Conf. on Modeling and Simulation of Microsystems, pp. 602–604, 2000.
Although maskless EUV lithography using SLMs remains a promising approach today, challenges prohibit practical and viable design and fabrication of SLMs for the EUV lithography systems. For example, conventional SLMs fabricated with spin-on deposited elastomer are not suitable for EUV applications because of difficulties in polishing soft materials. They also are not scalable to meet the requirements of existing EUV maskless lithography systems.
Clearly, there is a need in the art for a new design and fabrication of elastomer spatial light modulators that resolves these challenges and provides useful programmable masks for extreme ultraviolet lithography systems. The present invention addresses this need.